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Posted at 9:06 am, Tuesday, June 26, 2018
For several years, scientists have known that the coldest weather on Earth was nestled in the valleys near the top of the Antarctic ice sheet. Weather satellites have detected temperatures that could drop as low as minus 135 degrees (93 degrees Celsius).
But a new analysis of satellite data reveals that the coldest place on the planet is even more icy, and that temperatures plummet as low as near minus 148 (100 degrees Celsius) at night during the winter Antarctic.
The authors of the new study, published in Geophysical Research Letters, found "about 100" sites that displayed low temperatures of about minus 144 Celsius during the 2004-2016 winters. Most often, these temperatures, colder than the average temperature on Mars (around minus 76), were observed in troughs and valleys near the summit of the East Antarctic Ice Sheet. They occurred at altitudes of about 12,500 to 13,000 feet, mostly in July and August.
Before analysis of satellite data, the coldest temperature measured on Earth was minus 89 Celsius, recorded on the Eastern Antarctic shelf at the Russian station Vostok in July 1983. The analysis of satellite data published in 2013 analyzed 32 years of data from colder temperatures were present, closer to minus 135. This latest study recalibrated satellite data using more recent data on meteorological stations and concluded that the coldest temperatures were 5 degrees lower than that.
Locations where air less 144 was analyzed shared similar characteristics. "[T]They occurred in small cavities of 2 to 3 meters (6 to 9 feet) deep on the surface of the ice, on the south side of the high ridges of the plateau, "says the press release of the study.
Remarkably, the lowest temperatures observed at all these troughs on the ice cap were around minus 144, though some of them were spaced tens of miles apart. In other words, the scientists found that minus 144 seemed to represent the soil or the theoretical minimum for the cold.
Such a reading of the freezing temperature is possible only in very specific weather conditions, the study found. The sky must be clear and the wind calm so that any residual heat radiates away from the surface of the Earth in space. The must also be as dry as possible because the water vapor, which is a greenhouse gas, can retain heat in the atmosphere.
If the air was extremely dry for a long period of time, it is possible that the temperature is below -144, but not much. "There is a limit to the duration of the conditions that allow cooling at these ultra-low temperatures, and a limit to the amount of heat that you can actually cross, because the water vapor must be almost non-existent to emit from the heat of the surface to these temperatures, "said Ted Scambos, a scientist at the National Snow and Ice Data Center and lead author of the study.
Will global warming due to increasing concentrations of greenhouse gases in the atmosphere from human activity gradually increase the floor for this minimum temperature? Scambos says that it is possible.
"Going from the front, I think we could see that the lower limit could start to increase slowly because we put more carbon dioxide in the air, and the water vapor in the stratosphere begins to increase.
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